1. Field of the Invention
This invention relates in general to thermal printing apparatus for producing a copy or slave magnetic tape by bringing the slave tape into contact with a master tape so that the information on the master tape will be printed on the slave tape. The slave tape is heated to a temperature in the vicinity of the Curie point and the present invention relates to an improved printing apparatus wherein the stretch or shrinkage due to the temperature changes do not result in distortion in the information printed on the completed slave tape.
2. Description of the Prior Art
It is known in the prior art to transfer information recorded on a magnetic storage tape to a slave tape by bringing the slave and master tape into contact with each other and wherein the slave tape medium is heated to a temperature high enough to reduce the reluctivity so that accurate copying occurs.
The slave storage medium is made of materials such as chromium dioxide CrO.sub.2 which have a relatively low Curie point T.sub.c. Such material also has desirable characteristics in the thermal printing art. The material such as chromium dioxide has a constant reluctivity at temperatures lower than the Curie point but the reluctivity suddenly drops near the Curie point T.sub.c.
On the other hand, the master magnetic storage medium is made of materials such as gamma ferric oxide (.gamma.-Fe.sub.2 O.sub.3) or Fe-Co alloy, and these materials have a gradually sloping remnance characteristic that covers a large temperature range below the Curie point T.sub.c ' (T.sub.c &lt;&lt; T.sub.c ').
When copy or slave magnetic storage material CrO.sub.2 is heated to a temperature which is equal to or higher than the Curie point T.sub.c and is then brought into direct contact with the master magnetic storage medium, information recorded on the master magnetic storage medium will be directly transferred to the copy or slave magnetic storage medium.
Conventional slave or copy magnetic tape is formed of polyester resin film as a base which generally has the characteristic in that it shrinks during cooling after being heated. For this reason, if the pattern of the information on the master tape is printed on the slave tape without compensating the pattern on the slave tape would not be a direct copy of the original pattern on the master tape due to the shrinking characteristic of the copy or slave tape.